infer_freq not working (yet) with datetime64[s]

[kafitzgerald]

What happened?

We have upstream dev CI testing on geocat-comp that recently failed (NCAR/geocat-comp#681) because the dtype='datetime64[s]isn't handled byinfer_freq` yet in xarray. In particular this if statement looks like it needs to be generalized:

xarray/xarray/coding/frequencies.py

Line 91 in 2bedca4

if dtype == "datetime64[ns]":

What did you expect to happen?

infer_freq to handle a broader range of dtypes

Minimal Complete Verifiable Example

import xarray as xr
import numpy as np
import pandas as pd

time = pd.to_datetime(['2020-01-01', '2020-01-02', '2020-01-04'])
non_uniform = xr.Dataset(data_vars={'data': (('time'), np.arange(3))}, coords={'time': time})
xr.infer_freq(non_uniform['time'])

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/katelynw/miniconda3/envs/geocat_comp_build/lib/python3.12/site-packages/xarray/coding/frequencies.py", line 96, in infer_freq
    index = CFTimeIndex(index.values)
            ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/katelynw/miniconda3/envs/geocat_comp_build/lib/python3.12/site-packages/xarray/coding/cftimeindex.py", line 259, in __new__
    assert_all_valid_date_type(data)
  File "/Users/katelynw/miniconda3/envs/geocat_comp_build/lib/python3.12/site-packages/xarray/coding/cftimeindex.py", line 170, in assert_all_valid_date_type
    raise TypeError(
TypeError: CFTimeIndex requires cftime.datetime objects. Got object of <class 'numpy.datetime64'>.

Anything else we need to know?

Only happens with the dev versions of both pandas and xarray.

Environment

INSTALLED VERSIONS

commit: None
python: 3.12.8 | packaged by conda-forge | (main, Dec 5 2024, 14:19:53) [Clang 18.1.8 ]
python-bits: 64
OS: Darwin
OS-release: 21.6.0
machine: arm64
processor: arm
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: ('en_US', 'UTF-8')
libhdf5: 1.14.4
libnetcdf: 4.9.2

xarray: 2025.1.2.dev19+g2bedca4f
pandas: 3.0.0.dev0+1871.gc0c778bdb7
numpy: 1.26.4
scipy: 1.14.1
netCDF4: 1.7.2
pydap: None
h5netcdf: None
h5py: None
zarr: None
cftime: 1.6.4
nc_time_axis: None
iris: None
bottleneck: 1.4.2
dask: 2025.1.0
distributed: 2025.1.0
matplotlib: 3.10.0
cartopy: 0.24.0
seaborn: None
numbagg: None
fsspec: 2024.12.0
cupy: None
pint: 0.24.4
sparse: None
flox: None
numpy_groupies: None
setuptools: 75.8.0
pip: 25.0
conda: None
pytest: 8.3.4
mypy: None
IPython: None
sphinx: None

[kmuehlbauer]

@kafitzgerald Thanks for the report. Indeed, we need to relax those checks.

Would you mind testing your workflow against #9999? Thanks!

[kafitzgerald]

Thanks so much for the quick fix!

Working great now 😄